Plant-root growth promoting agent

ABSTRACT

Herein are disclosed, a plant-root growth promoting agent, which comprises inosine as the effective ingredient, as well as a method for promoting plant root growth, which comprise applying such plant-root growth promoting agent to the soil or, in the case of hydroponics, to the hydroponic water.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a growth promoting agent for the rootof a plant whose roots, stems and leaves can be distinguished each fromthe other two. More specifically, this invention relates to a plant-rootgrowth promoting agent comprising inosine as the effective ingredientand also to a method for promoting the root growth of such a plant,which method comprises applying inosine as the effective ingredientthereto, as well as to the plant bodies, including leaves of leafvegetables and fruit of fruit vegetables, of plants to which such aplant-root growth promoting agent has been applied during their lifetime.

2. Discussion of the Background

Several examples where a nucleic acid-related substance is applied toplants are conventionally known.

For example, in (a) Japanese Patent Publication kokoku No. 22919/1964 isdisclosed a plant growth regulator which comprises, as effectiveingredients, β-indoleacetic acid or the like and at least one substanceselected from the group consisting of a purine base, pyrimidine base,nucleoside and nucleotide, each available by the decomposition ofnucleic acid.

In the above plant growth regulator, however, nucleic acid bases,nucleosides and nucleotides which are obtained by the decomposition ofnucleic acid and differ in the decomposition degree are treated assubstances having the same effects (i.e., equivalents). As is apparentfrom the disclosure therein that these decomposition products of nucleicacid except some products belonging to purine base do not havesubstantial plant growth regulating action, the plant growth regulatoris a composition which requires, as the essential condition, thecombined use of a nucleic-acid decomposition product and β-indoleaceticacid or the like. In addition, the plant growth regulator is applied by(1) immersing seeds, radicles or seed tubers in a solution of theregulator; (2) spraying the solution to young fruit bodies of mushroom,young fruits, floral organs or phylloplanes; or (3) employing the abovetwo treatments in combination at appropriate times selected as needed(for example, subjecting seeds to the immersing treatment, and then thephylloplanes of the plants grown from the seeds to the sprayingtreatment), which treatments are utterly different from the applicationmethod according to the present invention in which the growth promotingagent is applied in such a way that it promotes directly the growth ofplant roots.

In (b) Japanese Patent Publication kokoku No. 16310/1974 is disclosed agrowth regulator for fruit vegetables which comprises, as effectiveingredients, a plant hormone such as chlorophenoxyacetic acid and atleast one substance selected from the group consisting of non-decomposednucleic acid pyrimidine bases, purine bases, nucleosides andnucleotides, the last four being obtainable by the decomposition ofnucleic acid.

In this growth regulator for fruit vegetables, however, non-decomposednucleic acid per se and various decomposition products thereof differentin decomposition degree are put in the same category and besides, as isapparent from the disclosure therein that these nucleic-acid relatedsubstances are used in order to reduce the generation of variousphysiological disorders of crops caused by the application of theabove-described plant hormone and to increase the expected effects to bebrought by the application of the plant hormone, the combined use of aplant hormone and a nucleic-acid related substance is the essentialcondition. In addition, a solution of the above growth regulator forfruit vegetables is desired to be distributed onto the plant body; thisdistribution treatment is effected at the flowering season to such anextent of wetting the flower clusters or flower organs with the solutionby spraying the solution with the use of a sprayer over the flowerclusters, the flower organs or the whole crop or by coating or immersingthe flower clusters or flower organs with or in the solution. Thesetreatments are utterly different from the application method of theplant-root growth promoting agent of the present invention.

In (c) Japanese Patent Publication kokoku No. 17670/1979 is disclosed amethod for improving the leaf life of a foliage plant, which comprisesbringing the leaves, the leaf stems or petioles, or the cut endsthereof, of a matured foliage plant into contact with one or more thanone of nucleotides and nucleosides (inosine being given as an example).

Also in the above method for improving the leaf life of a foliage plant,however, various nucleotides and nucleosides are put in the samecategory and a solution of effective ingredient(s) is applied asdescribed above, which application is utterly different from the methodaccording to the present invention.

In (d) Japanese Patent Application Laid-Open kokai No. 56759/1973 isdisclosed a method for promoting the germination of pollen of a fruittree, which comprises spraying the flower buds of the fruit tree at itsbud time with a single solution or a mixed solution of at least two ofnucleotides, nucleosides (inosine being given as an example) and nucleicacid bases.

Also in the above method for promoting the germination of pollen of afruit tree, however, various nucleotides and nucleosides are put in thesame category and in addition, a solution of the effective ingredient(s)is applied as described above, which application is utterly differentfrom the application method of the present invention.

In (e) Japanese Patent Laid-Open kokai No. 68848/1985 is disclosed amethod for prolonging the life of cut flowers, which comprising applyinga mixed solution of inosine and calcium chloride (as a liquid used fornatural flowers displayed at a flower shop or a liquid poured in aflower bowl or vase) onto natural flowers.

In the above method for prolonging the life of cut flowers, however, thecombined use of inosine and calcium chloride is the essential conditionand moreover, the application method of the effective ingredients isutterly different from that of the present invention.

As has been described above, the use of nucleic-acid related substancesfor plants is conventionally known, but in the said use, the combineduse of these substances with other substance is the essential condition.Even if various nucleic-acid related substances are used singly, theyare put in the same category without being distinguished from eachother. In addition, the application method of effective ingredients isutterly different from that of the present invention.

SUMMARY OF THE INVENTION

The growth of roots is an important basis for plants to grow further.Based on the sound growth of roots, the plant extends its leaves, putsforth flower buds, is pollinated, bears fruit, and enlarges the fruit.From such a viewpoint, there has accordingly been a demand for thedevelopment of a new substance or composition, or a new method ofpromoting the growth of plant roots.

An object of the present invention is therefore to provide a novelgrowth promoting agent composition for plant roots and a novel methodfor promoting the growth of plant roots.

With a view to attaining the above object and other objects, the presentinventor has carried out an extensive investigation and for the firsttime found that inosine has marked effects on the growth of roots of theaforesaid plants at large. Based on such findings, the invention hasbeen completed.

The present invention therefore relates to a plant-root growth promotingagent comprising inosine as the effective ingredient, a method forpromoting the growth of plant roots, which comprises applying such aplant-root growth promoting agent to the soil or, in the case ofhydroponics, to the hydroponic water, and to the plant bodies, includingleaves of leaf vegetables and fruit of fruit vegetables, of plants towhich such a plant-root growth promoting agent has been applied duringtheir life time.

By the terms "plant-root growth promoting" is meant in thisspecification that plant roots are increased in number, length (long orshort) and/or thickness (slender or corpulent), compared with caseswhere the plant-root growth promoting agent of the present invention isnot used, the other conditions being the same. The terms also includethe stimulation or promotion of plant root germination.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will hereinafter be described more specifically.

Plants to which the plant-root growth promoting agent of the presentinvention is to be applied can be those plants at large which haveclearly differentiated roots, stems and leaves, and specific examplesthereof include leaf vegetables, fruit vegetables, root vegetables,flowers, fruit trees and grains.

Inosine does not necessarily need to be a purified product. Insofar asit is free from side effects, an inosine product can be an inosinefermentation broth per se. Also, it can take the form such as aconcentrate or concentrated and dried product of an inosine fermentationbroth, a crude product of inosine separated from an inosine fermentationbroth, an inosine-containing intermediate treatment fraction upon thepreparation of a nucleic-acid related substance (nucleotide, nucleoside,nucleic acid base, etc.) by the decomposition of nucleic acid, aninosine-containing fraction of a processed inosine fermentation broth orthe like. It is needless to say that in the case where the applicationof inosine is carried out by adding it to hydroponic water, for thepurpose of preventing it from contaminating the hydroponic water,thereby causing putrefaction thereof, is preferred the application ofinosine in the form free from impurities which may cause pollution orputrefaction.

It is possible that the plant-root growth promoting agent containinginosine as the effective ingredient can be formed into a liquidpreparation in which the agent has been dissolved or dispersed in asuitable solvent such as water so as to carry out its applicationthrough soil or hydroponic water conveniently or can be formed into apowder or granular preparation by using a proper extender or binder.From the viewpoints of preventing putrefaction or increasing inosinesolubility, it is preferred to form inosine into its alkaline aqueoussolution which has been added with an inorganic alkali such as alkalimetal hydroxide, e.g., NaOH or KOH, alkaline earth metal hydroxide,e.g., Mg(OH)₂, or a basic amino acid such as lysine or arginine.Incidentally, when a K-containing compound such as KOH is used, the Kcomponent is also considered to have a good influence on the growth ofthe roots.

Examples of the application method of such a plant-root growth promotingagent include applying the agent to the soil in advance, then followedby sowing it with plant seeds, and adding the agent to hydroponic waterto dissolve the former in the latter in the case of hydroponiccultivation.

In addition, the agent can be useful for the purpose of recovering afruit vegetable such as strawberry or melon from the exhaustionattributed to fruit bearing, or preventing the fruit bearing exhaustion.And, other examples of the application method include applying the agentat a proper time during cultivation, for example, by adding to the soilat the roots of the fruit vegetable or by adding it to the hydroponicwater when the symptoms of bearing exhaustion are observed or whenbearing exhaustion is expected even if there are no actual symptomsthereof observed.

Proper application amounts vary with the time of application, the kindor cultivation density of the plant, growth or cultivation stage, or thelike. Anyway, it is to be noted in this connection that the plant-rootgrowth promoting agent according to the present invention is used in anamount which permits rooting (i.e., root germination) or root growthsuperior to those of a plant cultivated under the same conditions exceptthat the plant-root growth promoting agent of the present invention hasnot been applied. This amount can be determined by some preliminarycomparison test which is feasible by those skilled in the art. In thecase of soil before sowing, for example, the concentration of theinosine moiety can be as low as 5 to 50 g per 100 tons of soil (0.05 to0.5 ppm). In the case of hydroponic cultivation, the concentration ofinosine can be set at 0.1 to 2 ppm per hydroponic water, different fromthe case of the application to soil. The agent of the present inventiontherefore exhibits plant rooting action or plant-root growth promotingaction at such low concentrations.

Gibberellin which is one of representative plant hormones causesdisorders in the plant when the concentration is set wrongly, that is,set at too high a concentration, at the using time, while it has noeffects when the concentration is insufficient. This is commonly saidabout plant hormones.

In Japanese Patent Publication kokoku No. 16310/1974 referred to above,for example, harms brought by the application of a plant hormone aredescribed as follows: Chlorophenoxyacetic acid-based andβ-naphthoxyacetic acid-based compounds are known as so-called planthormones and application of them to, for example, fruit vegetables, iseffective for the growth promotion or fruit time acceleration of thefruit; On the other hand, however, there is a fear of these planthormones causing various physiological disorders of crops; Suchphysiological disorders include abnormal bending of the stems or leaves,shrinkage of the leaves, generation of callus on the stems, leaves orpeduncles, deformity of fruit, and frequent generation of hollow fruit.It is also described in the above literature that the object of theinvention concerned is to provide a fruit-vegetable growth regulatoruseful in agricultural management, based on the findings that thegeneration of the above-described physiological disorders can be reducedand at the same time expected effects can be heightened by the mixed useof chlorophenoxyacetic acid-based and/or β-naphthoxyacetic acid-basedcompound(s) and nucleic acid or decomposition product(s) thereof.

Compared with this, inosine is not a plant hormone, can be used atvarious application concentrations, does not cause any particulardisorders of the plant even used in an excess amount, is made use of bysoil microorganisms soon after application and does not cause anyobstacles but becomes useful for the soil improvement.

EXAMPLES

The present invention will hereinafter be described in detail byExamples.

Example 1

Preparation of Potted Strawberry Seedlings

In the preparation of strawberry seedlings, it is very important to keeptheir roots sound during a high-temperature summer season, because thestrawberry seedlings are allowed to grow in pots for a long time duringthis season. Any disorder or putrefaction of the roots has an adverseeffect on the subsequent growth after the seedlings are transplanted tothe garden, so farmers are most nervous about and also interested in thepreparation of potted seedlings out of all their strawberry cultivatingworks.

Water was sprayed onto potted seedlings of strawberry so as not to allowthe water in the pots to run out. Upon spraying, spraying of waterhaving inosine dissolved therein in an amount to give a concentration of0.05 to 0.5 ppm definitely contributed to the promotion of the growth ofthe roots (compared with those pots to which inosine-free water wassprayed). Described specifically, when roots are in direct contact witha water-impermeable vinyl or the like at the bottoms of the pots,putrefaction or disorders and blackening thereby of the roots are oftenobserved. The supply of inosine at the above concentration obviouslyreduced the damage and allowed many new white roots to appear. Thus, amarked difference was recognized compared with the case where inosinehad not been administered.

Example 2

Prevention of Bearing-Attributed Exhaustion of Strawberries

About three months after the harvesting of strawberries (i.e.,strawberry fruit) was started, symptoms showing bearing-attributedexhaustion were observed. Inosine was therefore applied as a solutionthereof in aqueous potassium hydroxide (pH 10.5) to the strawberryplants at their base (i.e., to the strawberry roots), together with alarge amount of water to give a concentration of 20 g per 10 ares (about100 tons of soil). As a result, the strawberries put forth new buds andleaves after several days, while the fruit buds of the strawberriesapproaching their thickening stage started steady growth. Although thekind of the strawberries tested has a tendency to very strong colordevelopment, shortage in coloring matter was not observed.

After that, the harvesting of strawberries was continued favorably.Supported by the sufficient development of leaves, the harvesting ofstrawberries could be continued until the beginning of June. Inaddition, until the end of July, runners were obtained from the aboveparent plants. Even in that season, the strawberries kept their leavessound with brisk runners.

Example 3

Prevention of Bearing-Attributed Exhaustion of Melons

After the first crop of melons named "PRINCE MELON" (Registered TradeMark) grown in a green house, an aqueous solution having inosinedissolved therein was administered to the melons at their base (i.e., tothe melon roots) to give a concentration of 20 g/10 ares. Only threedays after, a number of new white roots were observed to come to appearon the surface when the mulching was uncovered (compared therewith, in aplot where inosine had not been applied, new white roots were hardlyeven observed when the mulching was turned up). After that, new budsstarted to show marked growth, floral buds were put forth, and theflowers developed by pollination into fruit buds started thickening.

Such phenomena were also observed from melons grown outdoors. By theadministration of inosine to the plot where the melon vines did notcreep favorably due to the low temperatures, the melons revived and putforth many floral buds. Besides, thickening of the fruit wassatisfactory.

Example 4

Increase of Floral Buds of Lilies

Small-sized lily bulbs are cheap but put forth only one or two flowersper bulb when grown, while large-sized ones are expensive but put forthas many as four or five flowers per bulb.

So, some lily flower cultivators purchase small-sized lily bulbs fromlily bulb cultivators, and rear them into large-sized bulbs by cuttingoff flower buds from lily trees grown from such small-sized bulbs. Inthe following year, the lily flower cultivators plant such large-sizedbulbs, and ship the lily flowers put forth by the large-sized bulbs.

One year, small-sized bulbs of a lily named "RUREIBU" (Trade Mark) wereplanted. A solution of inosine was administered in an amount of 20 g per10 ares to the seedling roots, in order to make up for a little delay inpermanent planting and also to promote the growth of the seedlings. Theseedlings showed a favorable growth and their stems reached a sufficientheight. Contrary to expectation, they put forth as many as four floralbuds on the average, which were by two more than the ordinary case. Theflowers were large and magnificent.

Example 5

Cultivation of Brassica rapa var. pervidis

In the soil to which inosine had been administered in each amount asshown in Table 1 below, Brassica rapa var. pervidis, a kind of Chinesecabbage, was planted and 37 days after, it was harvested. The weight ofthe roots was weighed after heat-drying. To the control plot, no inosinewas added. Incidentally, the soil was prepared by sifting a soil calledKanumatsuchi through a 4-mesh sieve and then adding "Esusan Fertilizer",an amino-acid based, commercial fertilizer, ex Ajinomoto Co., Inc., tothe sifted soil of all the test plots, in an amount of 1200 mg per 400g-soil. Measurement results of the weight of the roots are showntogether in the table.

                  TABLE 1                                                         ______________________________________                                        Administered    Weight of the                                                                            Ratio                                              Amount (ppm)    roots (g)  (%)                                                ______________________________________                                        0 (Control plot)                                                                              0.19       100                                                0.05            0.28       147                                                0.1             0.27       142                                                0.2             0.33       174                                                0.3             0.29       153                                                0.5             0.45       237                                                ______________________________________                                    

As shown in Table 1, the roots of Brassica rapa var. pervidis showed amarked growth by the administration of inosine in an amount of at least0.05 ppm, preferably 0.5 ppm, relative to the soil.

A photograph of the water-washed roots of Brassica rapa var. pervidisharvested as described above was taken. Although this photograph doesnot clearly show the difference in the growth of the above-ground partsof Brassica rapa var. pervidis between the inosine-added plots and thecontrol plot, the growth in the test plots was superior to that of thecontrol plot in the subterranean parts, more specifically, superior inthe length and the number of the roots and moreover, in the quality ofthe above-ground parts (leaf part) as leaf vegetable. Thus, it has beenfound that the addition of inosine was effective even in an amount ofonly 5 to 20 g per 100 t of soil.

Example 6

Prevention of Damping-Off and Improvements in Sweetness Degree of Melons

In the case where late-autumn netted melon is subjected to fix plantingin early September in a warm district such as Kyushu, Japan, it cannotendure the thickening of the fruit in November or so at the harvest timeand often experiences damping-off in a moment. The damping-off causesawful damage and, for example, it usually damages all the melons in agreen house within as few as 2 to 3 days. The damping-off is presumed tooccur because if cultivation is continued without sufficient extensionof the roots at the warm time, demand for nutrients or water more thanexpected occurs at the thickening time of the fruit but the roots cannotmeet the demand.

In each of an inosine-applied plot and an inosine-free control plot ofthe same field, 10 seedlings of an EARLS series netted melon wereplanted. In the inosine-applied plot, 20 g per 10 ares (corresponding toabout 100 t of soil) of inosine were applied to the melon roots severaltimes, as an aqueous solution adjusted to pH 10.5 with potassiumhydroxide, together with a large amount of water at an early stage ofcultivation, and the melons were allowed to grow. As a result, 20 to 30%of the melon trees experienced damping-off. They did not, however, showcomplete death but partial death in their leaves. The melons kept alivewith withered leaves and 10 melons were harvested from the 10 trees.

On the other hand, in the control plot to which inosine had not beenapplied, many melon trees experienced damping-off. Six trees damped offcompletely, and harvested therefrom were four melons, which were lessthan half of the melons in the inosine-applied plot. Concerning thegrowth of the roots, the inosine-applied plot ((a)) was superior to thecontrol plot ((b): inosine-free plot (control plot)) in the thickness ofthe roots.

The inosine-applied plot was also higher in the sweetness degree (i.e.,sugar contents or Brix degree) of the fruit. Described specifically,three delicious-looking, fine-shaped melons were selected from themelons harvested from each of the inosine-applied plot and theinosine-free plot, and their sweetness degree was evaluated by 10people. As a result, all the members evaluated that the melons from theinosine-applied plot had stronger sweetness and were delicious comparedwith those from the control plot.

Example 7

Cultivation Test (in pots) of a Chrysanthemum coronarium

The cultivation test of a Chrysanthemum coronarium (a new root-spread,medium-sized leaved Chrysanthemum coronarium) was conducted by JapanFertilizers and Foods Association.

(a) Testing Method

Seedling raising pots (size: 9×7.5 cm, made of polyethylene) were filledwith soil to be tested, followed by the addition of a common fertilizerand water to artificially prepare a garden condition. When rooting wasrecognized after the seed sowing of the Chrysanthemum coronarium, apredetermined amount of an inosine solution was applied and theapplication effects on roots, above-ground parts such as stems andleaves were studied.

(b) Testing

(1) A 2% solution of inosine was applied after dilution with pure water.The application amount of each test plot is shown in Table 2 below.

                  TABLE 2                                                         ______________________________________                                        Test               Administered amount                                        plot               (per 100 t - soil)                                         ______________________________________                                        Standard amount     5 (g)                                                     2-fold amount      10                                                         4-fold amount      20                                                         6-fold amount      30                                                         10-fold amount     50                                                         ______________________________________                                    

(2) The progress including field husbandry is shown in Table 3 below.

                  TABLE 3                                                         ______________________________________                                        Events               Date                                                     ______________________________________                                        Pots filled with soil                                                                              December 1, 1996                                         Fertilized and watered                                                                             December 1, 1996                                         Sowing (10 seeds per pot)                                                                          December 1, 1996                                         Thinning out the seedlings                                                                         December 10 1996                                         to three                                                                      Inosine administered December 15, 1996                                        End of test, Observation                                                                           January 13, 1997                                         ______________________________________                                    

Incidentally, to all the test plots, aqueous solutions of monoammoniumphosphate, ammonium sulfate and potassium chloride were added in amountseach corresponding to 20 mg in terms of N, P₂ O₅ and K₂ O. Cultivationwas carried out in a heated green house. At the application time ofinosine, the seedlings had two leaves and reached a plant length of 5cm. The cultivation was conducted for 44 days in total, including 25days after the application of inosine.

(c) Test Results

Test results are shown in Table 4 below.

                                      TABLE 4                                     __________________________________________________________________________                       Above-ground parts (stems and leaves)                                                          Subterranean parts (roots)                Test pots      No. Weight (g) (Ratio)                                                                             Weight (g) (Ratio)                        __________________________________________________________________________    Inosine Administration                                                                  Standard                                                                           1   3.5              0.7                                                 amount                                                                             2   3.4              1.0                                                      3   3.4              0.8                                                      Average                                                                           3.43 (103)       0.83 (108)                                          2-fold                                                                             1   4.1              1.1                                                 amount                                                                             2   4.1              0.9                                                      3   3.7              1.2                                                      Average                                                                           3.97 (119)       1.07 (139)                                          4-fold                                                                             1   4.6              1.0                                                 amount                                                                             2   4.3              1.4                                                      3   4.4              1.3                                                      Average                                                                           4.43 (133)       1.23 (160)                                          6-fold                                                                             1   3.9              1.1                                                 amount                                                                             2   4.2              1.1                                                      3   4.4              1.1                                                      Average                                                                           4.17 (125)       1.10 (143)                                          10-fold                                                                            1   3.6              1.2                                                 amount                                                                             2   3.8              0.9                                                      3   3.9              1.0                                                      Average                                                                           3.77 (113)       1.03 (134)                                Non-administered pot                                                                         1   3.5              0.8                                       (Control pot)  2   3.0              0.7                                                      3   3.5              0.8                                                      Average                                                                           3.33 (100)       0.77 (100)                                __________________________________________________________________________

It is apparent that application effects of inosine are recognized in thegrowth of the roots and foliar (above-ground) parts of Chrysanthemumcoronarium.

Example 8

Cucumbers

In this example were employed pots and a bed soil exclusively used forraising seedlings, which were to show the application effects of inosineclearly.

(a) Test Method

"Sakata's Cell Pots (exclusively used for raising seedlings)" and a bedsoil exclusively used for cell pots, the filled amount being 17 g perpot, were employed as the pots and the bed soil. Neither the test plotsnor the control plot were subjected to fertilization. Inosine wasapplied three days after the beginning of germination. The seeds weresown on Sep. 19, 1996, inosine was applied on September 23, and theinvestigation on the harvest was carried out on October 1st.

(b) Designing of Test Plots

Test plots were designed as shown in Table 5 below.

                  TABLE 5                                                         ______________________________________                                        Test plots        Administration of inosine                                   ______________________________________                                        Control plot      --                                                          5 g inosine-per-10-are plot                                                                     8.5 ml of a 0.01 mg/dl                                                        solution                                                    20 g inosine-per-10-are plot                                                                    3.4 ml of a 0.1 mg/dl solution                              30 g inosine-per-10-are plot                                                                    5.1 ml of a 0.1 mg/dl solution                              50 g inosine-per-10-are plot                                                                    8.5 ml of a 0.1 mg/dl solution                              ______________________________________                                    

(c) Results

Results are shown in Table 6 below. Concerning each plot, theabove-ground parts (height and weight) and subterranean parts (rootweight) of 8 cucumber seedlings were measured and the average valueswere calculated, which are shown in Table 6 below. Incidentally, theroots were weighed after dried.

                  TABLE 6                                                         ______________________________________                                                  Check items                                                                   above-ground parts                                                                           subterranean parts                                   Test plots  height (ratio)                                                                          weight (ratio)                                                                           root weight (ratio)                          ______________________________________                                        Control plot                                                                               8.44(100)                                                                              0.91(100)  0.023(100)                                   5 g inosine-per-10-are                                                                    10.96(130)                                                                              0.97(107)  0.031(135)                                   plot                                                                          20 g inosine-per-10-                                                                      12.10(143)                                                                              1.06(116)  0.033(143)                                   are plot                                                                      30 g inosine-per-10-                                                                      11.72(139)                                                                              1.13(124)  0.026(113)                                   are plot                                                                      50 g inosine-per-10-                                                                      10.68(127)                                                                              1.02(112)  0.027(117)                                   are plot                                                                      ______________________________________                                         height unit: cm                                                               weight unit: g per sample                                                     root weight unit: g per sample                                           

It can be seen from the above table that the inosine-applied plots weresuperior to the control plot (inosine-application-free plot) in everyitem. Application of inosine in an amount of 20 to 30 g/10 ares ispresumed to be the most effective.

Example 9 Peas

Peas were subjected to the cultivation test in the same manner as inExample 8. Supposing that the weight of the combined vine and foliarweight and that of the roots of the control peas (application-free plot)were 100 each, the vine and foliar weights were 107 and 120 and the rootweights were 120 and 120 when inosine was applied in amounts of 30 g/10ares and 50 g/10 ares, respectively. Thus, application effects ofinosine were recognized.

EFFECTS OF THE INVENTION

The present invention has made it possible to carry out plant-rootgrowth promotion easily and, in turn, to carry out rearing or thickeningof leaves, floral buds, fruit bearing, or fruit easily.

What is claimed as new and desired to be secured by Letters Patent ofthe United Patents is:
 1. A method for promoting root growth of a plant,which comprises applying inosine to soil in an amount of 5-50 g per 100tons of soil (0.05-0.5 ppm), or to hydroponic water in a concentrationof 0.1-2 ppm based on the hydroponic water, the plant being in saidsoil, or in said hydroponic water, and being selected from the groupconsisting of leaf vegetables, fruit vegetables, root vegetables,flowers, fruit trees and grains.
 2. The method of claim 1, wherein saidinosine is applied to soil containing said plant.
 3. The method of claim1, wherein said inosine is applied to hydroponic water containing saidplant.
 4. The method of claim 1, wherein said inosine is applied in analkaline aqueous solution.
 5. The method of claim 4, wherein saidalkaline aqueous solution contains inorganic alkali.
 6. The method ofclaim 4, wherein said alkaline aqueous solution contains a basic aminoacid.
 7. The method of claim 5, wherein said inorganic alkali ispotassium hydroxide.
 8. The method of claim 1, wherein said plant is astrawberry or melon plant, and said method further treats fruit-bearingexhaustion of said plant.
 9. The method of claim 1, wherein said plantis a lily, and said method further increases floral buds of said lily.10. The method of claim 1, wherein said plant is a chinese cabbage. 11.The method of claim 8, wherein said plant is a melon plant, and saidmethod further increases sugar content of melons of said plant.
 12. Themethod of claim 1, wherein said plant is a chrysanthemum.
 13. The methodof claim 6, wherein said basic amino acid is lysine or arginine.